The present invention relates to reversible screwdrivers, and relates more particularly to such a reversible screwdriver which uses a socket and a rotating knob to control the working direction of the shaft.
A screwdriver is an important hand tool used for turning screws. However, conventional screwdrivers are inconvenient to use because the operator must lift the shaft from the workpiece upon each turn. Nowadays, various reversible ratchet screwdrivers have been disclosed, and have appeared on the market. These reversible ratchet screwdrivers can turn screws more efficiently because the handle runs idle when it is rotated in the reversed direction. FIG. 1 shows a reversible ratchet screwdriver according to the prior art. The handle of this reversible ratchet screwdriver comprises a chamber at one end, a plurality of slant grooves at two opposite ends of the chamber, a longitudinal center hole at the center of the bottom side of the chamber, and an arched groove on the bottom side of the chamber. A shaft is fastened to the chamber of the handle, having a bit coupling hole at one end for mounting a bit, and a ratchet wheel at an opposite end received inside the chamber of the handle. The ratchet wheel has a round rod at an outer side fitted into the longitudinal center hole of the handle. A locating plate is fastened to the arched groove of the handle to stop the shaft in place. Stop members are respectively and horizontally fastened to the slant grooves of the handle, each having a projecting tooth stopped between the ratchet wheel and the periphery of the chamber of the handle. A push block with a forked spring plate is mounted on the stop members. A socket is mounted around the shaft and fastened to the handle outside the chamber. By means of changing the position of the push block in the chamber, the working direction of the screwdriver is controlled. When the push block is moved to a predetermined position, the respective stop member is forced away, from the ratchet wheel by the forked spring plate of the push block, and therefore the ratchet wheel can be turned in one direction, and is prohibited from being turned in the reverse direction. When the push block is moved to the middle position, the ratchet wheel is locked and prohibited from rotary motion. This structure of reversible ratchet screwdriver is functional. However, the shaft tends to slip when the reversible ratchet screwdriver turns a big screw. Furthermore, this reversible ratchet screwdriver is not durable in use because the forked spring plate tends to be deformed.